In this work, the mechanism of enhanced photocatalysis of TiO2 with Fe3+ was studied using Sulfadiazine (SD) as the model compound. Results indicated that degradation rate of SD was enhanced by the addition of Fe3+ in TiO2 suspension. The crystalline structure of TiO2 particles was stable in suspensions. The hydroxyl radical generated by TiO2/Fe3+ (both TiO2 and Fe3+) photocatalysis was in a higher yield. Moreover, Fe2+ was found not to give an obvious impact on the SD degradation in TiO2 suspension, whereas Fe3+ had a notable effect. The adsorption amount of TiO2 was greatly enhanced by the addition of Fe3+ in suspensions. Finally, an interaction model of SD degradation in TiO2 suspension containing Fe3+ was also proposed by investigating of surface behaviors of TiO2 particles. It will be beneficial to use Fe3+ as the electron acceptors on the surface of TiO2 particles, which helps to improve the yield of hydroxyl radical. (C) 2011 Elsevier B.V. All rights reserved.